1. Field of the Invention
Embodiments of the present invention relate generally to bearing housings for supporting a variety of shafts, and more specifically to a bearing housing capable of use in wet and/or dry applications.
2. Background of Related Art
A variety of systems exist to support shafts in machinery. The Automotive industry uses, for example, and not limitation, plain bearings, ball bearings, and needles bearings. Plain bearings are used, for example, to support engine crankshafts and camshafts. These bearing are generally pressure fed lubricant, such as motor oil, such that the supported shaft is actually supported on a thin film of oil. Properly sized (i.e., clearanced) plain bearings are inexpensive and long lasting, but the requirement for pressurized lubrication makes them impractical for some applications.
Ball bearings and needle bearings, on the other hand, rely on multiple balls or cylinders disposed circumferentially around a shaft and contained by one or more bearing races. In this configuration, because the balls or needles are free to rotate, friction between the bearing and the shaft is reduced. As a result, while these bearings may use pressurized lubrication, they often function with only a packing of grease, or other heavy lubricant, to provide some lubrication and cooling. A type of roller bearing, known as a taper bearing, is often used for automotive wheel bearings, for example. Wheel bearings can be packed with grease and can run for tens of thousands of miles without maintenance.
The propeller shaft (“prop shaft”) on a boat or other aquatic vehicle, on the other hand, presents a unique challenge. This challenge is created by the fact that the shaft must be attached to the engine or transmission on one end and a propeller on the other end. This is challenging because, generally speaking, the engine is inside the vehicle and dry, while the propeller is obviously at least partially in the water. In addition, due to the layout of many aquatic vehicles, the prop shaft tends to be fairly long, requiring some support in the middle to prevent excessive deflection, or “whip.”
Conventional prop shaft bearings tend to be simple plain bearings that are constructed of brass, or some other metal, that has some lubricity. These bearings do not rotate with the shaft, however, and thus, rely on the shaft being submerged in water for cooling and lubrication. Because water provides only minimal lubrication, however, these bearing tend to have a limited service life. In addition, the service life can be further reduced if the bearing is operated out of the water for any significant length of time (i.e., more than a few seconds). This can nonetheless occur during, for example and not limitation, maintenance or use on an amphibious vehicle.
What is needed, therefore, is an improved, self-contained, self lubricating bearing system for prop, and other, shafts. The system should include an improved bearing housing capable of sealing lubricants in and water out. The system should also provide increased maintenance intervals and improved access for maintenance. It is to such a system that embodiments of the present invention are primarily directed.